A basic dictionary question
MRAB
python at mrabarnett.plus.com
Thu Jun 11 07:29:25 EDT 2015
On 2015-06-11 11:10, David Aldrich wrote:
> Hi
>
> I am fairly new to Python. I am writing some code that uses a
> dictionary to store definitions of hardware registers. Here is a small
> part of it:
>
> import sys
>
> register = {
>
> 'address' : 0x3001c,
>
> 'fields' : {
>
> 'FieldA' : {
>
> 'range' : (31,20),
>
> },
>
> 'FieldB' : {
>
> 'range' : (19,16),
>
> },
>
> },
>
> 'width' : 32
>
> };
>
> def main():
>
> fields = register['fields']
>
> for field, range_dir in fields: <== This line fails
>
> range_dir = field['range']
>
> x,y = range_dir['range']
>
> print(x, y)
>
> if __name__ == '__main__':
>
> main()
>
> I want the code to print the range of bits of each field defined in the
> dictionary.
>
> The output is:
>
> Traceback (most recent call last):
>
> File "testdir.py", line 32, in <module>
>
> main()
>
> File "testdir.py", line 26, in main
>
> for field, range_dir in fields:
>
> ValueError: too many values to unpack (expected 2)
>
> Please will someone explain what I am doing wrong?
>
You're iterating over the keys. What you want is to iterate over
"fields.items()" which gives the key/value pairs.
> Also I would like to ask how I could print the ranges in the order they
> are defined. Should I use a different dictionary class or could I add a
> field to the dictionary/list to achieve this?
>
Dicts are unordered. Try 'OrderedDict' from the 'collections' module.
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